The 31st Annual American Birkebeiner, takes place on Saturday, Feb. 21, 2004. Â It’s called the “Boston Marathon” of cross country skiing, is North America's largest and most prestigious cross-country ski marathon. Spanning 51 kilometers from Cable to Hayward, the Birkie is part of the esteemed Worldloppet series of 14 international races, part of the International Ski Federation (FIS) Marathon Cup series of eight races, and part of the American Ski Marathon series of 11 races. The event attracts 6,500 skiers from 19 foreign countries and 45 United States as well as 15,000 spectators to cheer them on.